aging AGM unusual behavior

papab
papab Registered Users Posts: 67 ✭✭
in Caravan, Recreational Vehicle, and Marine Power Systems #1
I have a 150 amp-hr lifeline AGM that is sulphated and less than 80% capacity.   It takes a long time to charge up.   I've decided to keep using it until it fails.
I've noticed a couple of times that after the current has dropped fairly low (~0.6 amps), sometimes the current will rise during absorption,.   What I have been doing when that happens is switching to float and sometimes equalizing.   This time I've decided to just leave it at the absorption voltage 14.2V for a while.   It's been there for about 18 hrs now, the battery is warm, but not hot (about 25C), and isn't making any noises.    What's going on inside?   Am I doing it good or destroying it?

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #2
    This thread has comments about Concorde (only) AGM battery recovery... (original thread was FLA--read around for the stuff you need):

    https://forum.solar-electric.com/discussion/351467/water-treatment-for-over-sulfation

    Section 5.6 in the Concorde manual:

    http://www.sunxtender.com/pdfs/Sun_Xtender_Battery_Technical_Manual.pdf

    Low current (5% of battery 24 hour capacity rating), will get to something like 15.5 volts (or even as high as 18 volts for a 12 volt battery) during this process... You need a battery charger that can hold 5% rate of charge >15.5 volts.

    Follow instructions.

    So--You probably are not "killing your battery"--But you could increase charging voltage (while holding 5% max current) and monitoring temperature. As long as temperature and current specs are not exceeded--Go for it.

    -Bill "not a battery expert/engineer at all" B.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #3
    I should also add, apparently the Concorde manual has had some major revisions over the last few years--You need to make sure you have the latest (Revision G is what I found).

    CoachDad has been having some poor life from Concorde, and has been getting multiple versions of the manual--Which apparently are pushing for "more charging" as many of the failures are from under charging the Concorde AGM batteries (and possibly AGM batteries in general).

    Marc Kurth, an engineer with lots of AGM/off grid system experience has been saying that most AGM failures (in his experience) are from under charging--Not over charging.

    This post has Marc's and CoachDad's posts:

    https://forum.solar-electric.com/discussion/comment/401425#Comment_401425

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • papab
    papab Registered Users Posts: 67 ✭✭
    edited September 2019 #4
    Thx, thats good info.   I don't have a constant current charger so I can't really follow that procedure.   I think I'll let it charge at 14.2 for a while and keep an eye on it.   What really hurt this battery is when I 1st got them I had a 2 week trip with not much sun and not enough driving time.  After that, many tries at equalizing never recovered it.    I think the lifeline/sunxtender batteries take longer to charge than most, and are more sensitive to partial state of charge.   The two weaknesses combine to make a lousy battery for me and for CoachDad.  
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  • Marc Kurth
    Marc Kurth Solar Expert Posts: 1,165 ✭✭✭✭
    #5
    BB. said:
    I should also add, apparently the Concorde manual has had some major revisions over the last few years--You need to make sure you have the latest (Revision G is what I found).

    CoachDad has been having some poor life from Concorde, and has been getting multiple versions of the manual--Which apparently are pushing for "more charging" as many of the failures are from under charging the Concorde AGM batteries (and possibly AGM batteries in general).

    Marc Kurth, an engineer with lots of AGM/off grid system experience has been saying that most AGM failures (in his experience) are from under charging--Not over charging.

    This post has Marc's and CoachDad's posts:

    https://forum.solar-electric.com/discussion/comment/401425#Comment_401425

    -Bill

    Bill, I am not an engineer - just a guy who has been specializing in this for the last 11-12 years.  I invite people to call Lifeline to verify my veracity!
    I have all of the tech manuals going back to 2008, and there have been very few changes over that time. The two that come to mind are a reduction in charging voltages: WAS 14.1v to 14.6v as an acceptable range for Absorb and Float was 13.1v to 13.6v.  About 8-9 years ago they dropped them to 14.2v-14.4v and 13.2v-13.4v.  NOT a big deal. They clearly pushed the fact that a fully charged battery only drew one half of one percent of the C/20 rating when charging at the absorb voltage.
    About 5-6 years ago, Concorde started suggesting equalizing when recovering from sulfation caused by undercharging. Eventually, that lead to suggesting equalizing more often if required.
    Think about this: The battery chemistry hasn't changed. The design/construction hasn't changed. So why the change in recommendation? The internet megaphone has been screaming that you will easily and quickly destroy your AGM's with overcharging, so people are afraid to let the charge cycle finish. The ONLY battery failure that I see from overcharging are caused by equipment failure, or people using the wrong settings. The required Absorb/Float settings are on the label of every battery.
    Concorde publishes absorb times (as a starting point for fine tuning) of 2 hrs. to 4 hrs. depending upon cycle depth.
    It takes quite awhile to ruin your 1,000 AH battery bank while charging it at the Absorb voltage, which equals 1,000 x .005 = 5 amp charge rate. It is important to remember that the sun goes down with extreme regularity each night.
    I always have more questions than answers. That's the nature of life.
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  • Marc Kurth
    Marc Kurth Solar Expert Posts: 1,165 ✭✭✭✭
    #6
    papab said:
    I have a 150 amp-hr lifeline AGM that is sulphated and less than 80% capacity.   It takes a long time to charge up.   I've decided to keep using it until it fails.
    I've noticed a couple of times that after the current has dropped fairly low (~0.6 amps), sometimes the current will rise during absorption,.   What I have been doing when that happens is switching to float and sometimes equalizing.   This time I've decided to just leave it at the absorption voltage 14.2V for a while.   It's been there for about 18 hrs now, the battery is warm, but not hot (about 25C), and isn't making any noises.    What's going on inside?   Am I doing it good or destroying it?


    Let's see of we can figure this one out!

    Basic info need for trouble shooting:
    Have you owned this battery since new?
    What is the two letter code on the small round white sticker?
    What are the first three digits on the label with the bar code?
    What has this battery been used for during the last few years?
    What brand/style/capacity is the charging system?
    What is the fully charged "standing voltage" - measured at least 4 hours after charging or discharging. 24-48 hours is OK too.

    You feel that it tales a long tome to charge. Tell me what makes you say this.
    How often are you equalizing? Define what your equalizing parameters are.
    Explain what makes you feel that the battery is sulfated?

    Marc
    I always have more questions than answers. That's the nature of life.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #7
    Sorry Marc. Engineer via the school of hard knocks?  :)

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • papab
    papab Registered Users Posts: 67 ✭✭
    #8
    Marc Kurth said:
    papab said:
    I have a 150 amp-hr lifeline AGM that is sulphated and less than 80% capacity.   It takes a long time to charge up.   I've decided to keep using it until it fails.
    I've noticed a couple of times that after the current has dropped fairly low (~0.6 amps), sometimes the current will rise during absorption,.   What I have been doing when that happens is switching to float and sometimes equalizing.   This time I've decided to just leave it at the absorption voltage 14.2V for a while.   It's been there for about 18 hrs now, the battery is warm, but not hot (about 25C), and isn't making any noises.    What's going on inside?   Am I doing it good or destroying it?


    Let's see of we can figure this one out!

    Basic info need for trouble shooting:
    Have you owned this battery since new?
    What is the two letter code on the small round white sticker?
    What are the first three digits on the label with the bar code?
    What has this battery been used for during the last few years?
    What brand/style/capacity is the charging system?
    What is the fully charged "standing voltage" - measured at least 4 hours after charging or discharging. 24-48 hours is OK too.

    You feel that it tales a long tome to charge. Tell me what makes you say this.
    How often are you equalizing? Define what your equalizing parameters are.
    Explain what makes you feel that the battery is sulfated?

    Marc
    Some background here, and I think answers to most of your questions:
    I did get the battery that was discussed in that thread pro-rated and replaced with a 125 ah 31XT in Feb 2017.   The new battery lasted about 1.5 years of light cycling and being very attentive to keeping it charged up.   It failed with completely different symptoms, a shorted cell, as diagnosed by Dave at Lifeline.    The cause for that failure is unknown, but my theory is that is was due to poor voltage/current control of the trimetric charge controller.   It was very unstable and they have improved it.    I won't use that SCC with a new battery though, it is still not very stable.   
    So... now I'm back to the sulphated 30H.  When the 31XT failed  (this summer), I reinstalled the 30H which they didn't want back & I had sitting in the corner of the garage (I charged it up occasionally). 
    Yes, owned since new.
    BO sticker
    Since I put it back in the camper van this summer, it is usually on the charger at 13.3, or on a 3-4 day camping trip where it is discharging to about 80% SOC overnight and getting back to 95-98%, with plenty of hours at absorption voltage (14.3-14.5), and a couple of hours at finish voltage (15-15.5V) (plenty of solar during the day where I camp).   Then plugged in when I get home.
    Xantrex trucharge 2 60 amp, and 150 W solar on the roof, 50 W portable, trimetric charge controller and battery monitor.
    I haven't let is sit long enough for a resting voltage measurement since I put it back in service.
    I don't have exact number but I think it takes about 8-10 hrs to return 105% from 20% discharge.
    I've been equalizing haphazardly after every camping trip.
    It's been at 14.3 V and 2.x amps for about 24 hrs.   Still not hot or making noises.   I switched it back to float, 13.3V just now.   The relatively high current for hours is puzzling to me, but maybe it is just the way it is for an 'old' battery?   As it is being charged up the current drops to around 1 amp, seems to stay around there for hours, before climbing to 2+
     
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  • Marc Kurth
    Marc Kurth Solar Expert Posts: 1,165 ✭✭✭✭
    #9
    We really do need to know what the standing voltage is. We are diagnosing a battery that was condemned by the factory a few years ago. It is now almost 5 years old and has spent the last couple of years sitting in your garage, with an occasional charge.
    It doesn't sound like you ever figured out what actually happened to the 30H in 2016?
    Yes, the end amps will shift upward with age. Forcing the system to stay at the full absorb voltage for long periods of time, slowly cooks the battery and causes a very slow and gradual venting. This is one way to overcharge an AGM. For the same reason, I am also not a fan of a finishing charge at a forced  current that is higher than the battery's natural current draw - except when trying correct for some deficiency in charging. Note that your Xantrex charger doesn't do that.
    Again, I see 2,000 to 2,500 of their batteries in service, every year. The batteries that achieve a long life are,charged per the manufacturers instructions. For RV's, 5 years is minimum and 7-9 is not unusual. 
    Lastly, I am not a fan of battery monitoring systems to determine SOC. Yes, they can very accurately measure current, but: The 102% to 110% return amps depends on battery age, battery temperature, depth of discharge and rate of charge. Additionally, if the battery is dried out and/or sulfated, its capacity has changed. It is essentially a moving target.
    Marc




    I always have more questions than answers. That's the nature of life.
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,889 ✭✭✭✭✭✭
    #10
    Adding to Marc my experience as an engineer, and not that it matters here, is many of these battery problems can be easily avoided by "seeing" the charge cycle. This is critical on small solar systems because loads, clouds, and as Marc said the day ending interfere in getting a full charge.

    Below is a neighbors FLA battery going through a 3 hour Absorb and a 1 hour EQ. You can see at no time does the charge voltage drop below the set-point.

    A shunt and a battery monitor are a waste of money on an AGM or FLA. Not worth the work either.


    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • papab
    papab Registered Users Posts: 67 ✭✭
    edited September 2019 #11
    Mark, The 30HT was sulphated because I didn't realize how important it was to charge it up every day, or every couple of days, and how important the 14.3 absorption voltage was.   Vacationing in BC, cloudy, rainy, I had it charging from the van system which usually put out 14.1V, and it was a little chilly so it probably should have been 14.5V.   It always very slow to charge, and got slower every day.   It never got below 50 or 60%, but probably didn't get to 100% for a couple of weeks.    Even under controlled, carefully monitored conditions at home on the xantrex.   The 31XT never charged up as quickly as lifeline claims it does either, based upon their suggested 0.5%C finish amps.  
    Dave & Mark,  How can you see the charge cycle without a current shunt?  If you're only looking at voltage, you're only seeing part of it.  How can you determine if you're charging up too much or too little?  
    Mark, what charger or monitor did you using to record and plot that data?


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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,889 ✭✭✭✭✭✭
    #12
    It is easy to "see" but only if you use Schneider Electric inverter chargers XW & CSW. They determine battery current and load current internally. Alot of other things also :)

    To limit the charge current is a setting on a decent charger.

    I think the Radian can do this from Outback but I can't remember.
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • Marc Kurth
    Marc Kurth Solar Expert Posts: 1,165 ✭✭✭✭
    edited September 2019 #13
    @papab Per my post, I am not challenging the accuracy of current measurement across a good shunt resistor - it 's the State of Charge inaccuracies that I have a serious problem with, for the reasons that I explained above. Knowing the charging current is critical to help understand what s happenng.
    I have seen WAAAAY too many battery bank failures because the owner trusted the % SOC reading from their battery monitoring system. It often goes like this:
    Customer: "My battery bank is suffering a capacity loss."
    Me: "What is your standing voltage?"
    Customer: "I don't know, but my expensive monitor says 100%."
    Me: "Please get a standing voltage reading."
    Customer: "OK, it's showing 100% and the voltage is 49.2v."
    Me: "Your battery bank severely undercharged."
    Customer: "No way, it reads 100% SOC every day."
    Marc
    I always have more questions than answers. That's the nature of life.
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  • papab
    papab Registered Users Posts: 67 ✭✭
    #14
    I understand that battery monitors cannot always be trusted.  I use finish amps and returned percent as recommended by by the manufacturer as the final word.

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    edited September 2019 #15
    And Absorb & Float voltage setpoints too. Time on absorb is important too--But if you have the correct voltage(s) and ending amps--Time should be OK. 

    -Bill "just an observation by a non-expert" B.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • papab
    papab Registered Users Posts: 67 ✭✭
    #16
    14.3 and 13.3
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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,101 ✭✭✭✭✭
    edited September 2019 #17
    papab said:
    14.3 and 13.3

     
    AGM batteries are all over the place when it comes to charging voltages. As an example these have a cycle duty charge voltage of up to 15 volts. Voltage limits this high for AGM batteries was unheard of in the past. 

    Hopefully the info. on the battery is visable. That's the best photo I have.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,889 ✭✭✭✭✭✭
    #18
    I don't see the end amps? Without that it is the same age old problem of an AGM being undercharged and dying before it's time.
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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